The present invention relates generally to a navigation system including a road map display showing a road map and guiding the vehicle through a preset driving route. More specifically, the invention relates to a navigation system which automatically locates the navigation start and end points in response to entry of the vehicle position and destination position.
In recent years, various vehicular navigation systems for guiding vehicles through present travelling routes have been developed. Some navigation systems include a map display on a display monitor, such as a CRT display. In such systems, map data are stored in a high-capacity map memory, such as a CD ROM or the like. The map memory is generally divided into a plurality of pages representing separate, contiguous map areas. Each map area is further divided into a plurality of map blocks which generally correspond to one screen-ful on the display monitor. Each map area and/or map block includes an identification code or number.
Due to the relatively voluminous data stored in the map memory, it is sometimes difficult to access the appropriate map block including the vehicle starting point and the destination. Some systems allow automatic access to the appropriate map block by means of manual entry of the rough position of the starting point and the destination. Even in such cases, when a large number of map blocks are later isotropically searched for suitable route point, search time tends to be unacceptably long. On the other hand, when the scanning area is limited, it sometimes happens that the appropriate map block can not be found due to errors in the map data.